package com.widgetgrid.android.arimagesearch.zxing;

import java.util.Hashtable;
import java.util.Vector;

public class PointPatternFinder {
	  private static final int CENTER_QUORUM = 2;
	  protected static final int MIN_SKIP = 3; // 1 pixel/module times 3 modules/center
	  protected static final int MAX_MODULES = 57; // support up to version 10 for mobile clients
	  private static final int INTEGER_MATH_SHIFT = 8;

	  private final BitMatrix image;
	  private final Vector possibleCenters;
	  private boolean hasSkipped;
	  private final int[] crossCheckStateCount;
	  private final PointPatternCallback resultPointCallback;

	  /**
	   * <p>Creates a finder that will search the image for three finder patterns.</p>
	   *
	   * @param image image to search
	   */
	  public PointPatternFinder(BitMatrix image) {
	    this(image, null);
	  }

	  public PointPatternFinder(BitMatrix image, PointPatternCallback resultPointCallback) {
	    this.image = image;
	    this.possibleCenters = new Vector();
	    this.crossCheckStateCount = new int[5];
	    this.resultPointCallback = resultPointCallback;
	  }

	  protected BitMatrix getImage() {
	    return image;
	  }

	  protected Vector getPossibleCenters() {
	    return possibleCenters;
	  }

	  PointInfoObject find() {
	    int maxI = image.getHeight();
	    int maxJ = image.getWidth();
	    // We are looking for black/white/black/white/black modules in
	    // 1:1:3:1:1 ratio; this tracks the number of such modules seen so far

	    // Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
	    // image, and then account for the center being 3 modules in size. This gives the smallest
	    // number of pixels the center could be, so skip this often. When trying harder, look for all
	    // QR versions regardless of how dense they are.
	    int iSkip = (3 * maxI) / (4 * MAX_MODULES);
	    if (iSkip < MIN_SKIP) {
	      iSkip = MIN_SKIP;
	    }

	    boolean done = false;
	    int[] stateCount = new int[5];
	    for (int i = iSkip - 1; i < maxI && !done; i += iSkip) {
	      // Get a row of black/white values
	      stateCount[0] = 0;
	      stateCount[1] = 0;
	      stateCount[2] = 0;
	      stateCount[3] = 0;
	      stateCount[4] = 0;
	      int currentState = 0;
	      for (int j = 0; j < maxJ; j++) {
	        if (image.get(j, i)) {
	          // Black pixel
	          if ((currentState & 1) == 1) { // Counting white pixels
	            currentState++;
	          }
	          stateCount[currentState]++;
	        } else { // White pixel
	          if ((currentState & 1) == 0) { // Counting black pixels
	            if (currentState == 4) { // A winner?
	              if (foundPatternCross(stateCount)) { // Yes
	                boolean confirmed = handlePossibleCenter(stateCount, i, j);
	                if (confirmed) {
	                  // Start examining every other line. Checking each line turned out to be too
	                  // expensive and didn't improve performance.
	                  iSkip = 2;
	                  if (hasSkipped) {
	                    done = haveMultiplyConfirmedCenters();
	                  } else {
	                    int rowSkip = findRowSkip();
	                    if (rowSkip > stateCount[2]) {
	                      // Skip rows between row of lower confirmed center
	                      // and top of presumed third confirmed center
	                      // but back up a bit to get a full chance of detecting
	                      // it, entire width of center of finder pattern

	                      // Skip by rowSkip, but back off by stateCount[2] (size of last center
	                      // of pattern we saw) to be conservative, and also back off by iSkip which
	                      // is about to be re-added
	                      i += rowSkip - stateCount[2] - iSkip;
	                      j = maxJ - 1;
	                    }
	                  }
	                } else {
	                  // Advance to next black pixel
	                  do {
	                    j++;
	                  } while (j < maxJ && !image.get(j, i));
	                  j--; // back up to that last white pixel
	                }
	                // Clear state to start looking again
	                currentState = 0;
	                stateCount[0] = 0;
	                stateCount[1] = 0;
	                stateCount[2] = 0;
	                stateCount[3] = 0;
	                stateCount[4] = 0;
	              } else { // No, shift counts back by two
	                stateCount[0] = stateCount[2];
	                stateCount[1] = stateCount[3];
	                stateCount[2] = stateCount[4];
	                stateCount[3] = 1;
	                stateCount[4] = 0;
	                currentState = 3;
	              }
	            } else {
	              stateCount[++currentState]++;
	            }
	          } else { // Counting white pixels
	            stateCount[currentState]++;
	          }
	        }
	      }
	      if (foundPatternCross(stateCount)) {
	        boolean confirmed = handlePossibleCenter(stateCount, i, maxJ);
	        if (confirmed) {
	          iSkip = stateCount[0];
	          if (hasSkipped) {
	            // Found a third one
	            done = haveMultiplyConfirmedCenters();
	          }
	        }
	      }
	    }

	    PointPattern[] patternInfo = selectBestPatterns();
	    PointPattern.orderBestPatterns(patternInfo);

	    return new PointInfoObject(patternInfo);
	  }

	  /**
	   * Given a count of black/white/black/white/black pixels just seen and an end position,
	   * figures the location of the center of this run.
	   */
	  private static float centerFromEnd(int[] stateCount, int end) {
	    return (float) (end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0f;
	  }

	  /**
	   * @param stateCount count of black/white/black/white/black pixels just read
	   * @return true iff the proportions of the counts is close enough to the 1/1/3/1/1 ratios
	   *         used by finder patterns to be considered a match
	   */
	  protected static boolean foundPatternCross(int[] stateCount) {
	    int totalModuleSize = 0;
	    for (int i = 0; i < 5; i++) {
	      int count = stateCount[i];
	      if (count == 0) {
	        return false;
	      }
	      totalModuleSize += count;
	    }
	    if (totalModuleSize < 7) {
	      return false;
	    }
	    int moduleSize = (totalModuleSize << INTEGER_MATH_SHIFT) / 7;
	    int maxVariance = moduleSize / 2;
	    // Allow less than 50% variance from 1-1-3-1-1 proportions
	    return Math.abs(moduleSize - (stateCount[0] << INTEGER_MATH_SHIFT)) < maxVariance &&
	        Math.abs(moduleSize - (stateCount[1] << INTEGER_MATH_SHIFT)) < maxVariance &&
	        Math.abs(3 * moduleSize - (stateCount[2] << INTEGER_MATH_SHIFT)) < 3 * maxVariance &&
	        Math.abs(moduleSize - (stateCount[3] << INTEGER_MATH_SHIFT)) < maxVariance &&
	        Math.abs(moduleSize - (stateCount[4] << INTEGER_MATH_SHIFT)) < maxVariance;
	  }

	  private int[] getCrossCheckStateCount() {
	    crossCheckStateCount[0] = 0;
	    crossCheckStateCount[1] = 0;
	    crossCheckStateCount[2] = 0;
	    crossCheckStateCount[3] = 0;
	    crossCheckStateCount[4] = 0;
	    return crossCheckStateCount;
	  }

	  /**
	   * <p>After a horizontal scan finds a potential finder pattern, this method
	   * "cross-checks" by scanning down vertically through the center of the possible
	   * finder pattern to see if the same proportion is detected.</p>
	   *
	   * @param startI row where a finder pattern was detected
	   * @param centerJ center of the section that appears to cross a finder pattern
	   * @param maxCount maximum reasonable number of modules that should be
	   * observed in any reading state, based on the results of the horizontal scan
	   * @return vertical center of finder pattern, or {@link Float#NaN} if not found
	   */
	  private float crossCheckVertical(int startI, int centerJ, int maxCount,
	      int originalStateCountTotal) {
	    BitMatrix image = this.image;

	    int maxI = image.getHeight();
	    int[] stateCount = getCrossCheckStateCount();

	    // Start counting up from center
	    int i = startI;
	    while (i >= 0 && image.get(centerJ, i)) {
	      stateCount[2]++;
	      i--;
	    }
	    if (i < 0) {
	      return Float.NaN;
	    }
	    while (i >= 0 && !image.get(centerJ, i) && stateCount[1] <= maxCount) {
	      stateCount[1]++;
	      i--;
	    }
	    // If already too many modules in this state or ran off the edge:
	    if (i < 0 || stateCount[1] > maxCount) {
	      return Float.NaN;
	    }
	    while (i >= 0 && image.get(centerJ, i) && stateCount[0] <= maxCount) {
	      stateCount[0]++;
	      i--;
	    }
	    if (stateCount[0] > maxCount) {
	      return Float.NaN;
	    }

	    // Now also count down from center
	    i = startI + 1;
	    while (i < maxI && image.get(centerJ, i)) {
	      stateCount[2]++;
	      i++;
	    }
	    if (i == maxI) {
	      return Float.NaN;
	    }
	    while (i < maxI && !image.get(centerJ, i) && stateCount[3] < maxCount) {
	      stateCount[3]++;
	      i++;
	    }
	    if (i == maxI || stateCount[3] >= maxCount) {
	      return Float.NaN;
	    }
	    while (i < maxI && image.get(centerJ, i) && stateCount[4] < maxCount) {
	      stateCount[4]++;
	      i++;
	    }
	    if (stateCount[4] >= maxCount) {
	      return Float.NaN;
	    }

	    // If we found a finder-pattern-like section, but its size is more than 40% different than
	    // the original, assume it's a false positive
	    int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
	        stateCount[4];
	    if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal) {
	      return Float.NaN;
	    }

	    return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : Float.NaN;
	  }

	  /**
	   * <p>Like {@link #crossCheckVertical(int, int, int, int)}, and in fact is basically identical,
	   * except it reads horizontally instead of vertically. This is used to cross-cross
	   * check a vertical cross check and locate the real center of the alignment pattern.</p>
	   */
	  private float crossCheckHorizontal(int startJ, int centerI, int maxCount,
	      int originalStateCountTotal) {
	    BitMatrix image = this.image;

	    int maxJ = image.getWidth();
	    int[] stateCount = getCrossCheckStateCount();

	    int j = startJ;
	    while (j >= 0 && image.get(j, centerI)) {
	      stateCount[2]++;
	      j--;
	    }
	    if (j < 0) {
	      return Float.NaN;
	    }
	    while (j >= 0 && !image.get(j, centerI) && stateCount[1] <= maxCount) {
	      stateCount[1]++;
	      j--;
	    }
	    if (j < 0 || stateCount[1] > maxCount) {
	      return Float.NaN;
	    }
	    while (j >= 0 && image.get(j, centerI) && stateCount[0] <= maxCount) {
	      stateCount[0]++;
	      j--;
	    }
	    if (stateCount[0] > maxCount) {
	      return Float.NaN;
	    }

	    j = startJ + 1;
	    while (j < maxJ && image.get(j, centerI)) {
	      stateCount[2]++;
	      j++;
	    }
	    if (j == maxJ) {
	      return Float.NaN;
	    }
	    while (j < maxJ && !image.get(j, centerI) && stateCount[3] < maxCount) {
	      stateCount[3]++;
	      j++;
	    }
	    if (j == maxJ || stateCount[3] >= maxCount) {
	      return Float.NaN;
	    }
	    while (j < maxJ && image.get(j, centerI) && stateCount[4] < maxCount) {
	      stateCount[4]++;
	      j++;
	    }
	    if (stateCount[4] >= maxCount) {
	      return Float.NaN;
	    }

	    // If we found a finder-pattern-like section, but its size is significantly different than
	    // the original, assume it's a false positive
	    int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
	        stateCount[4];
	    if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal) {
	      return Float.NaN;
	    }

	    return foundPatternCross(stateCount) ? centerFromEnd(stateCount, j) : Float.NaN;
	  }

	  /**
	   * <p>This is called when a horizontal scan finds a possible alignment pattern. It will
	   * cross check with a vertical scan, and if successful, will, ah, cross-cross-check
	   * with another horizontal scan. This is needed primarily to locate the real horizontal
	   * center of the pattern in cases of extreme skew.</p>
	   *
	   * <p>If that succeeds the finder pattern location is added to a list that tracks
	   * the number of times each location has been nearly-matched as a finder pattern.
	   * Each additional find is more evidence that the location is in fact a finder
	   * pattern center
	   *
	   * @param stateCount reading state module counts from horizontal scan
	   * @param i row where finder pattern may be found
	   * @param j end of possible finder pattern in row
	   * @return true if a finder pattern candidate was found this time
	   */
	  protected boolean handlePossibleCenter(int[] stateCount, int i, int j) {
	    int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
	        stateCount[4];
	    float centerJ = centerFromEnd(stateCount, j);
	    float centerI = crossCheckVertical(i, (int)centerJ, stateCount[2], stateCountTotal);
	    if (!Float.isNaN(centerI)) {
	      // Re-cross check
	      centerJ = crossCheckHorizontal((int) centerJ, (int) centerI, stateCount[2], stateCountTotal);
	      if (!Float.isNaN(centerJ)) {
	        float estimatedModuleSize = (float) stateCountTotal / 7.0f;
	        boolean found = false;
	        int max = possibleCenters.size();
	        for (int index = 0; index < max; index++) {
	          PointPattern center = (PointPattern) possibleCenters.elementAt(index);
	          // Look for about the same center and module size:
	          if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {
	            center.incrementCount();
	            found = true;
	            break;
	          }
	        }
	        if (!found) {
	          PointPattern point = new PointPattern((int)centerJ, (int)centerI, estimatedModuleSize);
	          possibleCenters.addElement(point);
	          if (resultPointCallback != null) {
	            resultPointCallback.foundPossiblePointPattern(point);
	          }
	        }
	        return true;
	      }
	    }
	    return false;
	  }

	  /**
	   * @return number of rows we could safely skip during scanning, based on the first
	   *         two finder patterns that have been located. In some cases their position will
	   *         allow us to infer that the third pattern must lie below a certain point farther
	   *         down in the image.
	   */
	  private int findRowSkip() {
	    int max = possibleCenters.size();
	    if (max <= 1) {
	      return 0;
	    }
	    PointPattern firstConfirmedCenter = null;
	    for (int i = 0; i < max; i++) {
	    	PointPattern center = (PointPattern) possibleCenters.elementAt(i);
	      if (center.getCount() >= CENTER_QUORUM) {
	        if (firstConfirmedCenter == null) {
	          firstConfirmedCenter = center;
	        } else {
	          // We have two confirmed centers
	          // How far down can we skip before resuming looking for the next
	          // pattern? In the worst case, only the difference between the
	          // difference in the x / y coordinates of the two centers.
	          // This is the case where you find top left last.
	          hasSkipped = true;
	          return (int) (Math.abs(firstConfirmedCenter.getX() - center.getX()) -
	              Math.abs(firstConfirmedCenter.getY() - center.getY())) / 2;
	        }
	      }
	    }
	    return 0;
	  }

	  /**
	   * @return true iff we have found at least 3 finder patterns that have been detected
	   *         at least {@link #CENTER_QUORUM} times each, and, the estimated module size of the
	   *         candidates is "pretty similar"
	   */
	  private boolean haveMultiplyConfirmedCenters() {
	    int confirmedCount = 0;
	    float totalModuleSize = 0.0f;
	    int max = possibleCenters.size();
	    for (int i = 0; i < max; i++) {
	    	PointPattern pattern = (PointPattern) possibleCenters.elementAt(i);
	      if (pattern.getCount() >= CENTER_QUORUM) {
	        confirmedCount++;
	        totalModuleSize += pattern.getEstimatedModuleSize();
	      }
	    }
	    if (confirmedCount < 3) {
	      return false;
	    }
	    // OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
	    // and that we need to keep looking. We detect this by asking if the estimated module sizes
	    // vary too much. We arbitrarily say that when the total deviation from average exceeds
	    // 5% of the total module size estimates, it's too much.
	    float average = totalModuleSize / (float) max;
	    float totalDeviation = 0.0f;
	    for (int i = 0; i < max; i++) {
	    	PointPattern pattern = (PointPattern) possibleCenters.elementAt(i);
	      totalDeviation += Math.abs(pattern.getEstimatedModuleSize() - average);
	    }
	    return totalDeviation <= 0.05f * totalModuleSize;
	  }

	  /**
	   * @return the 3 best {@link FinderPattern}s from our list of candidates. The "best" are
	   *         those that have been detected at least {@link #CENTER_QUORUM} times, and whose module
	   *         size differs from the average among those patterns the least
	   * @throws ReaderException if 3 such finder patterns do not exist
	   */
	  private PointPattern[] selectBestPatterns() {

	    int startSize = possibleCenters.size();
	    if (startSize < 3) {
	      // Couldn't find enough finder patterns
	      return null;
	    }

	    // Filter outlier possibilities whose module size is too different
	    if (startSize > 3) {
	      // But we can only afford to do so if we have at least 4 possibilities to choose from
	      float totalModuleSize = 0.0f;
	      for (int i = 0; i < startSize; i++) {
	        totalModuleSize += ((PointPattern) possibleCenters.elementAt(i)).getEstimatedModuleSize();
	      }
	      float average = totalModuleSize / (float) startSize;
	      for (int i = 0; i < possibleCenters.size() && possibleCenters.size() > 3; i++) {
	    	PointPattern pattern = (PointPattern) possibleCenters.elementAt(i);
	        if (Math.abs(pattern.getEstimatedModuleSize() - average) > 0.2f * average) {
	          possibleCenters.removeElementAt(i);
	          i--;
	        }
	      }
	    }

	    if (possibleCenters.size() > 3) {
	      // Throw away all but those first size candidate points we found.
	      Collections.insertionSort(possibleCenters, new CenterComparator());      
	      possibleCenters.setSize(3);
	    }

	    return new PointPattern[]{
	        (PointPattern) possibleCenters.elementAt(0),
	        (PointPattern) possibleCenters.elementAt(1),
	        (PointPattern) possibleCenters.elementAt(2)
	    };
	  }
	  
  private static class CenterComparator implements Comparator {
    public int compare(Object center1, Object center2) {
      return ((PointPattern) center2).getCount() - ((PointPattern) center1).getCount();
    }
  }
}
